Laminated composite assemblies are frequently used in aircraft construction, and have branched into other areas of technology as well. Typically, the laminated composite assembly is formed of various laminates of a material, such as carbon fiber, which are formed into a single assembly under pressure and heat with the laminates being bonded by a resin. The resulting assembly provides great strength while also having great flexibility and light weight.
In the past, the materials have been placed between two rigid formed dies to provide the proper compression to form the final assembly. However, the making of a male and female mating die set is very costly and becomes prohibitive for small production runs of a particular assembly.
In another technique, a single die is employed which has a formed die face. The materials to be laminated are positioned on the die face and the assembly is encased within an air tight container, commonly a flexible plastic like material. The space between the bag and the materials to be laminated is filled with a number of hard balls, commonly made of aluminum. A vacuum is drawn from the bag so that the exterior pressure forces the bag against the balls, and the balls in turn provide a relatively uniform pressure acting against the materials to be laminated and forces those materials against the die face. The effect can be enhanced by placing the entire package within an autoclave and increasing the exterior pressure acting on the bag. The autoclave can also be heated to provide activation of the resin binding the material, forming the final assembly.
However, the use of a vacuum bag has substantial disadvantages. Most significantly, if any leak develops through the bag, the interior of the bag will be pressurized to the pressure of the autoclave, eliminating the pressure differential necessary for proper pressure lamination of the materials. Therefore, an improved method of forming such assemblies is desirable.